1. Field of the Invention
The present invention relates to a tablet for producing a one-sided sealing-type semiconductor device, comprising an epoxy resin composition with suppression in the generation of bowing and high reliability, a wafer with a resin layer and a semiconductor device produced by using the tablet.
2. Discussion of the Related Art
Conventionally, a cured resin layer is formed on one side of a wafer comprising a plural projected electrodes by subjecting a tablet comprising an epoxy resin composition to hot press molding, wherein the epoxy resin composition is obtained by cold pressing molding. However, in the wafer with a resin layer in which a cured resin layer is formed by using the tablet described above, there arises a problem that bowing is generated. Specifically, when a cured resin layer is formed by using the above-mentioned tablet, the bowing of the wafer with a resin layer is undesirably caused because the physical properties such as a coefficient of linear expansion of a cured product of an epoxy resin composition, which is the cured resin layer, are different from those of a wafer. The wafer with a resin layer in which the bowing described above is generated causes troubles during conveying and dicing, and has a defect that its applicability to the substrate becomes poor. Further, there also arise some problems that a stress is generated at the interface of the wafer and the cured resin layer, so that its reliability is impaired.
In addition, in the technique of packaging (sealing) a semiconductor element in the field of semiconductor devices in the recent years, one-sided sealing-type semiconductor devices, for instance, have been remarked and actually used. A semiconductor device in which a semiconductor element is sealed by a cured product of an epoxy resin composition has excellent mass-producibility and low costs. Further, the above-mentioned one-sided sealing type semiconductor device can have high performance by highly integrating the semiconductor element. In addition, in a method of mounting a semiconductor element to a board, which is the insulating substrate mentioned above in a flip chip manner or a direct chip attachment manner, sealing is usually carried out by one-sided sealing in a state of incorporating the semiconductor element, or alternatively by filling a molten thermosetting resin composition in a void between the insulating substrate and the semiconductor device and curing the composition. However, these semiconductor devices have some problems of generation of bowing of the package caused by curing shrinkage of a sealing resin, and incongruence in the coefficients of linear expansion of the insulating substrate and the sealing resin (cured product). In the semiconductor device in which the bowing described above is generated, pealing or the like is caused at the sealing interface by the stress due to bowing, so that its reliability is lowered, thereby resulting in poor applicability to a substrate. Therefore, a solution to such a problem is desired.
An object of the present invention to provide a tablet comprising an epoxy resin composition for producing a one-sided sealing-type semiconductor device with suppression in the generation of bowing and high reliability.
Another object of the present invention is to provide a wafer and a semiconductor device produced by using a tablet comprising an epoxy resin composition, and processes for producing the tablet and the wafer.
Still another object of the present invention is to provide a method of preventing generation of bowing of the wafer and the semiconductor device.
Still another object of the present invention is to provide a use of a tablet comprising an epoxy resin composition for preventing generation of bowing of the wafer and the semiconductor device.
These and other objects of the present invention will be apparent from the following description.
The present inventors have again studied on causation of bowing of the wafer with a resin layer from various angles. As a result, they have found that an amount reduced by heating of the tablet before molding is one of causations of bowing as well as conventionally known causations of curing shrinkage of the cured resin layer and incongruence in coefficients of linear expansion of the wafer and the cured resin layer. It is thought that the shrinkage of the resin is caused by exhalation of volatile components remaining in the internal of the cured resin layer when pressure-releasing.
The same can be said for the causations of bowing of the package. As a result of further studies based on these findings, in order to suppress the generation of the above-mentioned bowing, the present inventors have found that it is effective to reduce volatile components in the tablet usable for formation of the cured resin layer of a wafer with a resin layer, or the volatile components in the tablet before curing usable for sealing a semiconductor element on the insulating substrate, and to diminish the amount reduced by heating the tablet. Therefore, the present inventors have found that by using a tablet having an amount reduced by heating lower than a specified amount of the volatile components, the shrinkage of the resin due to exhalation when pressure-releasing can be suppressed, whereby the generation of bowing can be consequently suppressed. Also, the semiconductor device obtained by using the above-mentioned tablet of course has high reliability with suppression in the generation of bowing.
In addition, the present inventors have found that by using as the tablet one obtained by preparing a molten product comprising an epoxy resin composition and cooling and solidifying the molten product, the compression ratio of the tablet is made large and the resin of the tablet is made very dense, so that the tablet is less likely to be hygroscopic, whereby a tablet having a small amount reduced by heating can be obtained. Therefore, they have found that when a tablet of which compression ratio is very high and cured product has a glass transition temperature of not less than a particular value is used, a semiconductor device with more effective suppression of the generation of bowing and high reliability can be obtained. Further, they have found that a semiconductor device having high reliability can be obtained because the voids in the molded product can be reduced by having a low volatile component content and a high compression ratio. The present invention has been accomplished based on these findings.
Concretely, the present invention pertains to the following:
(1) a tablet for producing a semiconductor device with substantially no bowing, comprising an epoxy resin composition comprising an epoxy resin and a curing agent, wherein the tablet has the following characteristic (A):
(A): an amount reduced by heating being less than 0.05% by weight;
(2) the tablet according to item (1) above, obtainable by a process comprising preparing a molten product of the epoxy resin composition in an uncured state, and thereafter cooling and solidifying the molten product;
(3) the tablet according to item (1) or (2) above, further having at least one characteristic selected from the group consisting of:
(B): a compression ratio of the tablet being 98% or more; and
(C): a glass transition temperature of a cured product of the tablet being 120xc2x0 C. or more;
(4) a wafer with a resin layer comprising a plural projected electrodes and a cured resin layer formed on a projected electrode-mounting side of the wafer, wherein the cured resin layer is formed by the tablet of any one of items (1) to (3) above;
(5) a semiconductor device obtainable by a process comprising dicing the wafer with a resin layer of item (4) above into a given size;
(6) a semiconductor device comprising an insulating substrate, a semiconductor element mounted on one side of the insulating substrate, and a cured product of an epoxy resin composition, the semiconductor element being incorporated in and sealed by the cured product, wherein the cured product of an epoxy resin composition is formed by the tablet of any one of items (1) to (3) above;
(7) a semiconductor device comprising an insulating substrate, a semiconductor element mounted on one side of the insulating substrate via a plural connecting electrodes, and a cured resin layer sealing a void between the insulating substrate and the semiconductor element, wherein the cured resin layer is formed by the tablet of any one of items (1) to (3) above;
(8) a process for producing a wafer with a resin layer comprising a plural projected electrodes and a cured resin layer formed on a projected electrode-mounting side of the wafer, comprising the steps of putting the tablet of any one of items (1) to (3) above on the projected electrode-mounting side of the wafer, and heating the tablet to be melt-cured, thereby forming the cured resin layer;
(9) a process for producing a semiconductor device comprising an insulating substrate, a semiconductor element mounted on one side of the insulating substrate, and a cured product of an epoxy resin composition, the semiconductor element being incorporated in and sealed by the cured product, comprising the steps of putting the tablet of any one of items (1) to (3) above on the semiconductor element, and heating the tablet to be melt-cured, thereby forming the cured product;
(10) a process for producing a semiconductor device comprising an insulating substrate, a semiconductor element mounted on one side of the insulating substrate via a plural connecting electrodes, and a cured resin layer sealing a void between the insulating substrate and the semiconductor element, comprising the steps of heat-melting the tablet of any one of items (1) to (3) above, and filling the void and curing the tablet, thereby forming the cured resin layer;
(11) a method for preventing generation of bowing of a wafer, comprising forming a cured resin layer on a wafer by using the tablet of any one of items (1) to (3) above;
(12) a method for preventing generation of bowing of a semiconductor device, comprising sealing semiconductor elements on one side of an insulating substrate by using the tablet of any one of items (1) to (3) above;
(13) use of a tablet of any one of items (1) to (3) above for preventing generation of bowing of a wafer in the production of the wafer in which a cured resin layer is formed on the wafer; and
(14) use of a tablet of any one of items (1) to (3) above for preventing generation of bowing of a semiconductor device in the production of the semiconductor device in which semiconductor elements are sealed on one side of an insulating substrate.